Dental caries is initiated by the demineralization of hard tissue of the teeth usually by organic acids produced from fermentation of dietary sugar by dental plaque odontopathogenic bacteria. Dental caries is still a major public health problem. Further, restored tooth surfaces can be susceptible to further dental caries around the margins of the restoration. Even though the prevalence of dental caries has decreased through the use of fluoride in most developed countries, the disease remains a major public health problem. Dental erosion/corrosion is the loss of tooth mineral by dietary or regurgitated acids. Dental hypersensitivity is due to exposed dentinal tubules through loss of the protective mineralized layer, cementum and dental calculus is the unwanted accretion of calcium phosphate minerals on the tooth surface. All these conditions, dental caries, dental erosion/corrosion, dental hypersensitivity and dental calculus are therefore imbalances in the level of calcium phosphates. Dental caries, dental erosion/corrosion and dental hypersensitivity can be treated with stabilized amorphous calcium phosphate (ACP) by providing bioavailable calcium and phosphate ions to replace the lost calcium phosphate mineral. Stabilized ACP can also bind to the surface of dental calculus and prevent further accretion. Stabilized ACP and stabilized amorphous calcium fluoride phosphate (ACFP) therefore can play a major role in preventing and treating oral diseases and other medical conditions.
Casein is present in milk in the form of micelles, which are believed to be roughly spherical particles with a radius of about 100 nm, dispersed in a continuous phase of water, salt, lactose and whey proteins. The casein micelles serve as a carrier of calcium phosphate providing a bioavailable source of calcium and phosphate ions for bone and teeth formation. The ability of casein micelles to maintain calcium and phosphate ions in a soluble and bioavailable state is retained by the tryptic multiphosphorylated peptides of the caseins known as the casein phosphopeptides (CPP). WO 98/40406 describes casein phosphopeptide-amorphous calcium phosphate complexes (CPP-ACP) and CPP-stabilised amorphous calcium fluoride phosphate complexes (CPP-ACFP) which have been produced at alkaline pH. Such complexes have been shown to prevent enamel demineralization and promote remineralization of enamel subsurface lesions in animal and human in situ caries models.
The phosphopeptides which are active in forming the complexes do so whether or not they are part of a full-length casein protein. The active casein phosphopeptides (CPP) formed by tryptic digestion have been specified in U.S. Pat. No. 5,015,628 and include peptides Bos αs1-casein X-5P (f59-79) [1], Bos βcasein X-4P (f1-25) [2], Bos αs2-casein X-4P (f46-70) [3] and Bos αs2-casein X-4P (f1-21) [4] as follows:
[1]Gln59-Met-Glu-Ala-Glu-Ser(P)-Ile-Ser(P)-Ser(P)-Ser(P)-Glu-Glu-Ile-Val-Pro-Asn-Ser(P)-Val-Glu-Gln-Lys79 αs1(59-79)(SEQ ID NO: 1) [2]Arg1-Glu-Leu-Glu-Glu-Leu-Asn-Val-Pro-Gly-Glu-Ile-Val-Glu-Ser(P)-Leu-Ser(P)-Ser(P)-Ser(P)-Glu-Glu-Ser-Ile-Thr-Arg25 β(1-25)(SEQ ID NO: 2) [3]Asn46-Ala-Asn-Glu-Glu-Glu-Tyr-Ser-Ile-Gly-Ser(P)-Ser(P)-Ser(P)-Glu-Glu-Ser(P)-Ala-Glu-Val-Ala-Thr-Glu-Glu-Val-Lys70αs2(46-70)(SEQ ID NO: 3) [4]Lys1-Asn-Thr-Met-Glu-His-Val-Ser(P)-Ser(P)-Ser(P)-Glu-Glu-Ser-Ile-Ile-Ser(P)-Gln-Glu-Thr-Tyr-Lys21 αs2(1-21)(SEQ ID NO: 4)
Other casein phosphopeptides that have activity in assisting in the stabilization of superloaded amorphous calcium phosphate complexes are those peptides containing the sequences Ser(P)-Xaa-Glu/Ser(P) where Ser(P) represents a phosphoseryl residue. Therefore the phosphopeptides/phosphoproteins active in stabilizing superloaded amorphous calcium phosphate and amorphous calcium fluoride phosphate complexes are those containing the sequence -A-B-C-, where A is a phosphamino acid, preferably phosphoserine; B is any amino acid including a phosphoamino acid and C is one of the glutamate, aspartate or a phosphoamino acid (SEQ ID NO:5).
Amorphous calcium phosphate stabilized by casein phosphopeptides as described in WO 98/40406 is available commercially in a product sold as Recaldent™ as provided by Recaldent Pty Ltd, Victoria, Australia. However, it would be desirable for an even more effective form of amorphous calcium phosphate stabilized by casein phosphopeptides to be available for treatments. Further, when Recaldent™ is dissolved in a carrier such as distilled water, there is inevitable leakage of ions into the surrounding water to form an equilibrium. This will, in some uses, reduce the calcium phosphate deliverable by the composition, such as for a treatment.